1. Field of the Invention
The present invention relates to a circuit for protecting an electrical and/or electronic system, and more particularly, to a circuit for removing an external low-voltage noise signal applied to an electrical and/or electronic system.
2. Description of the Related Art
Noise that affects electronic components flows in through a power line that supplies power to an electric and/or electronic system and a signal line that receives and outputs an electrical signal from and to the electric and/or electronic system. Accordingly, a noise preventing circuit for protecting the electrical and/or electronic system from noise is connected to the power line and the signal line. The noise preventing circuit is required by almost all electronic products, such as, computers, image apparatuses, acoustic apparatuses, all controllers that control electronic products, etc.
Noise signals coming via the power line or the signal line are generally blocked by a low pass filter (LPF), a high pass filter (HPF), or a noise filter. Each of these filters is generally made up of a resistor (R), an inductor (L), and a capacitor (C). Accordingly, these filters are quite big and expensive. This impedes the miniaturization and popularization of electronic apparatuses. In particular, there is a limit to reduction of the sizes of the filters. In addition, there is a problem in that both the LPF and HPF must be installed at a single power or signal line.
Furthermore, these filters cannot remove a low-voltage noise signal, such as, a room temperature noise signal. The low-voltage noise signal has a voltage lower than a rated signal voltage or a rated power voltage. Examples of the low-voltage noise signal include a noise signal that hinders production of clear sounds and clean images, a noise signal that prevents precise recognition of the low value of a digital signal, an RF signal noise that is applied to a power or supply line, etc.